Observation of metal-organic interphase in Cu-based electrochemical CO2-to-ethanol conversion

Interphases are critical in electrochemical systems, influencing performance by controlling ion transport and stability. This study explores a metal-organic interphase in the electrocatalytic reduction of CO2 (CO2RR) on Cu, extending the concept of interphases to CO2 conversion. Investigating organic modifications on CuOx, we discover metal-organic interphases over 10 nm thick in highly ethanol-selective systems, contrary to the expected monolayer adsorption. Using an automated platform, 1080 CO2RR experiments with 180 molecular modifiers identify functional groups affecting selectivity for ethanol and multi-carbon (C2+) products. We find that these modifiers consistently produce metal-organic interphases on the Cu or CuOx surface. These interphases modulate Cu coordination, CO2RR intermediates, and interfacial water configuration, significantly improving electrocatalytic performance. Testing across 11 CuOx-based catalysts validates this approach, culminating in the development of two electrocatalysts that achieve ~80% faradaic efficiency for C2+ products with ethanol partial current densities up to 328 and 507 mA cm−2. This study highlights the pivotal role of interphases in CO2RR, advancing CO2 conversion technologies. Interphases are crucial in electrochemical systems, but their role in CO2 electroreduction remains underexplored. Here, the authors report their importance in improving electrocatalytic performance by systematically investigating 180 molecular modifiers using an automatic electrocatalysis platform.